Generally, sub-sea hydrocarbon production is maintained at or near wellhead production temperature for ease of transport and processing. However, for oil and/or gas wells in deeper water, often far off-shore, the constant cooling effect of ocean water makes it difficult to maintain wellhead production temperatures without accruing expensive pipeline heating and/or insulating costs. As such, production from such sub-sea wells becomes economically unfeasible, especially for smaller reservoirs. Likewise, the cost of large surface facilities for processing warm production is substantial in deep water and can generally only be justified for relatively large hydrocarbon reservoirs. In addition, heating of a cooler flow using equipment on a floating structure is substantially more costly than heating the flow at a shore-based facility.
Equipment and controls for current undersea well production and processing are most often located at least in part on large floating processing structures, and/or drilling vessel structures. Floating structures in deep water and fixed structures in relatively shallow water are subject to the surface effects of storms and other natural events. Production risers to surface structures are likewise more subject to natural and intentional trauma. In addition, conventional structures are subject to accidental, or in rare cases intentional, damage by surface vessels, or the like. Generally, such floating structures are large and incur relatively substantial expense to drill, complete, work-over, process, and the like for such wells. Relative to shore-based facilities, floating structures are significantly more costly to operate on a per square foot basis or per unit weight basis.
One conventional solution for reducing the volumetric amount of well product that is transported through a pipeline, and therefore reducing the volumetric amount of product requiring heating, or other means, is to process the well product and remove undesirable components prior to transportation through the pipeline, water being an example. Equipment is installed on the ocean floor to process the well product and reduce the volumetric amount, and cost, of transport. Expensive equipment and controls are required for such processing.
Another conventional solution involves the addition of a variety of chemicals at or near the well-head to offset the negative effects of cooling effluents, such as the formation of sticky solids, waxes, gas hydrates, and the like that can slow or block flow. The additional cost, requirements of storage, and requirements for injection means of such chemicals, as well as removal of such chemicals during processing, can also add considerable expense to production.